crypto/dsa/dsa_ossl.c

   1 /* crypto/dsa/dsa_ossl.c */
   2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58
  59 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
  60
  61 #include <stdio.h>
  62 #include "cryptlib.h"
  63 #include <openssl/bn.h>
  64 #include <openssl/sha.h>
  65 #include <openssl/dsa.h>
  66 #include <openssl/rand.h>
  67 #include <openssl/asn1.h>
  68 #ifdef OPENSSL_FIPS
  69 #include <openssl/fips.h>
  70 #endif
  71
  72 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
  73 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
  74 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
  75                          DSA *dsa);
  76 static int dsa_init(DSA *dsa);
  77 static int dsa_finish(DSA *dsa);
  78
  79 static DSA_METHOD openssl_dsa_meth = {
  80 "OpenSSL DSA method",
  81 dsa_do_sign,
  82 dsa_sign_setup,
  83 dsa_do_verify,
  84 NULL, /* dsa_mod_exp, */
  85 NULL, /* dsa_bn_mod_exp, */
  86 dsa_init,
  87 dsa_finish,
  88 DSA_FLAG_FIPS_METHOD,
  89 NULL,
  90 NULL,
  91 NULL
  92 };
  93
  94 /* These macro wrappers replace attempts to use the dsa_mod_exp() and
  95  * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
  96  * having a the macro work as an expression by bundling an "err_instr". So;
  97  *
  98  *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
  99  *                 dsa->method_mont_p)) goto err;
 100  *
 101  * can be replaced by;
 102  *
 103  *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
 104  *                 dsa->method_mont_p);
 105  */
 106
 107 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
 108         do { \
 109         int _tmp_res53; \
 110         if((dsa)->meth->dsa_mod_exp) \
 111                 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
 112                                 (a2), (p2), (m), (ctx), (in_mont)); \
 113         else \
 114                 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
 115                                 (m), (ctx), (in_mont)); \
 116         if(!_tmp_res53) err_instr; \
 117         } while(0)
 118 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
 119         do { \
 120         int _tmp_res53; \
 121         if((dsa)->meth->bn_mod_exp) \
 122                 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
 123                                 (m), (ctx), (m_ctx)); \
 124         else \
 125                 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
 126         if(!_tmp_res53) err_instr; \
 127         } while(0)
 128
 129 const DSA_METHOD *DSA_OpenSSL(void)
 130 {
 131         return &openssl_dsa_meth;
 132 }
 133
 134 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 135         {
 136         BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
 137         BIGNUM m;
 138         BIGNUM xr;
 139         BN_CTX *ctx=NULL;
 140         int reason=ERR_R_BN_LIB;
 141         DSA_SIG *ret=NULL;
 142         int noredo = 0;
 143
 144 #ifdef OPENSSL_FIPS
 145         if(FIPS_selftest_failed())
 146             {
 147             FIPSerr(FIPS_F_DSA_DO_SIGN,FIPS_R_FIPS_SELFTEST_FAILED);
 148             return NULL;
 149             }
 150
 151         if (FIPS_mode() && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
 152                 {
 153                 DSAerr(DSA_F_DSA_DO_SIGN, DSA_R_KEY_SIZE_TOO_SMALL);
 154                 return NULL;
 155                 }
 156 #endif
 157
 158         BN_init(&m);
 159         BN_init(&xr);
 160
 161         if (!dsa->p || !dsa->q || !dsa->g)
 162                 {
 163                 reason=DSA_R_MISSING_PARAMETERS;
 164                 goto err;
 165                 }
 166
 167         s=BN_new();
 168         if (s == NULL) goto err;
 169         ctx=BN_CTX_new();
 170         if (ctx == NULL) goto err;
 171 redo:
 172         if ((dsa->kinv == NULL) || (dsa->r == NULL))
 173                 {
 174                 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
 175                 }
 176         else
 177                 {
 178                 kinv=dsa->kinv;
 179                 dsa->kinv=NULL;
 180                 r=dsa->r;
 181                 dsa->r=NULL;
 182                 noredo = 1;
 183                 }
 184
 185
 186         if (dlen > BN_num_bytes(dsa->q))
 187                 /* if the digest length is greater than the size of q use the
 188                  * BN_num_bits(dsa->q) leftmost bits of the digest, see
 189                  * fips 186-3, 4.2 */
 190                 dlen = BN_num_bytes(dsa->q);
 191         if (BN_bin2bn(dgst,dlen,&m) == NULL)
 192                 goto err;
 193
 194         /* Compute  s = inv(k) (m + xr) mod q */
 195         if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
 196         if (!BN_add(s, &xr, &m)) goto err;              /* s = m + xr */
 197         if (BN_cmp(s,dsa->q) > 0)
 198                 if (!BN_sub(s,s,dsa->q)) goto err;
 199         if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
 200
 201         ret=DSA_SIG_new();
 202         if (ret == NULL) goto err;
 203         /* Redo if r or s is zero as required by FIPS 186-3: this is
 204          * very unlikely.
 205          */
 206         if (BN_is_zero(r) || BN_is_zero(s))
 207                 {
 208                 if (noredo)
 209                         {
 210                         reason = DSA_R_NEED_NEW_SETUP_VALUES;
 211                         goto err;
 212                         }
 213                 goto redo;
 214                 }
 215         ret->r = r;
 216         ret->s = s;
 217
 218 err:
 219         if (!ret)
 220                 {
 221                 DSAerr(DSA_F_DSA_DO_SIGN,reason);
 222                 BN_free(r);
 223                 BN_free(s);
 224                 }
 225         if (ctx != NULL) BN_CTX_free(ctx);
 226         BN_clear_free(&m);
 227         BN_clear_free(&xr);
 228         if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
 229             BN_clear_free(kinv);
 230         return(ret);
 231         }
 232
 233 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
 234         {
 235         BN_CTX *ctx;
 236         BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
 237         int ret=0;
 238
 239         if (!dsa->p || !dsa->q || !dsa->g)
 240                 {
 241                 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
 242                 return 0;
 243                 }
 244
 245         BN_init(&k);
 246         BN_init(&kq);
 247
 248         if (ctx_in == NULL)
 249                 {
 250                 if ((ctx=BN_CTX_new()) == NULL) goto err;
 251                 }
 252         else
 253                 ctx=ctx_in;
 254
 255         if ((r=BN_new()) == NULL) goto err;
 256
 257         /* Get random k */
 258         do
 259                 if (!BN_rand_range(&k, dsa->q)) goto err;
 260         while (BN_is_zero(&k));
 261         if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
 262                 {
 263                 BN_set_flags(&k, BN_FLG_CONSTTIME);
 264                 }
 265
 266         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 267                 {
 268                 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 269                                                 CRYPTO_LOCK_DSA,
 270                                                 dsa->p, ctx))
 271                         goto err;
 272                 }
 273
 274         /* Compute r = (g^k mod p) mod q */
 275
 276         if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
 277                 {
 278                 if (!BN_copy(&kq, &k)) goto err;
 279
 280                 /* We do not want timing information to leak the length of k,
 281                  * so we compute g^k using an equivalent exponent of fixed length.
 282                  *
 283                  * (This is a kludge that we need because the BN_mod_exp_mont()
 284                  * does not let us specify the desired timing behaviour.) */
 285
 286                 if (!BN_add(&kq, &kq, dsa->q)) goto err;
 287                 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
 288                         {
 289                         if (!BN_add(&kq, &kq, dsa->q)) goto err;
 290                         }
 291
 292                 K = &kq;
 293                 }
 294         else
 295                 {
 296                 K = &k;
 297                 }
 298         DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
 299                         dsa->method_mont_p);
 300         if (!BN_mod(r,r,dsa->q,ctx)) goto err;
 301
 302         /* Compute  part of 's = inv(k) (m + xr) mod q' */
 303         if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
 304
 305         if (*kinvp != NULL) BN_clear_free(*kinvp);
 306         *kinvp=kinv;
 307         kinv=NULL;
 308         if (*rp != NULL) BN_clear_free(*rp);
 309         *rp=r;
 310         ret=1;
 311 err:
 312         if (!ret)
 313                 {
 314                 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
 315                 if (r != NULL)
 316                         BN_clear_free(r);
 317                 }
 318         if (ctx_in == NULL) BN_CTX_free(ctx);
 319         BN_clear_free(&k);
 320         BN_clear_free(&kq);
 321         return(ret);
 322         }
 323
 324 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
 325                          DSA *dsa)
 326         {
 327         BN_CTX *ctx;
 328         BIGNUM u1,u2,t1;
 329         BN_MONT_CTX *mont=NULL;
 330         int ret = -1, i;
 331         if (!dsa->p || !dsa->q || !dsa->g)
 332                 {
 333                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
 334                 return -1;
 335                 }
 336
 337         i = BN_num_bits(dsa->q);
 338         /* fips 186-3 allows only different sizes for q */
 339         if (i != 160 && i != 224 && i != 256)
 340                 {
 341                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
 342                 return -1;
 343                 }
 344
 345 #ifdef OPENSSL_FIPS
 346         if(FIPS_selftest_failed())
 347             {
 348             FIPSerr(FIPS_F_DSA_DO_VERIFY,FIPS_R_FIPS_SELFTEST_FAILED);
 349             return -1;
 350             }
 351
 352         if (FIPS_mode() && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
 353                 {
 354                 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_KEY_SIZE_TOO_SMALL);
 355                 return -1;
 356                 }
 357 #endif
 358
 359         if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
 360                 {
 361                 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
 362                 return -1;
 363                 }
 364         BN_init(&u1);
 365         BN_init(&u2);
 366         BN_init(&t1);
 367
 368         if ((ctx=BN_CTX_new()) == NULL) goto err;
 369
 370         if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 371             BN_ucmp(sig->r, dsa->q) >= 0)
 372                 {
 373                 ret = 0;
 374                 goto err;
 375                 }
 376         if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 377             BN_ucmp(sig->s, dsa->q) >= 0)
 378                 {
 379                 ret = 0;
 380                 goto err;
 381                 }
 382
 383         /* Calculate W = inv(S) mod Q
 384          * save W in u2 */
 385         if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
 386
 387         /* save M in u1 */
 388         if (dgst_len > (i >> 3))
 389                 /* if the digest length is greater than the size of q use the
 390                  * BN_num_bits(dsa->q) leftmost bits of the digest, see
 391                  * fips 186-3, 4.2 */
 392                 dgst_len = (i >> 3);
 393         if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
 394
 395         /* u1 = M * w mod q */
 396         if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
 397
 398         /* u2 = r * w mod q */
 399         if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
 400
 401
 402         if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
 403                 {
 404                 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 405                                         CRYPTO_LOCK_DSA, dsa->p, ctx);
 406                 if (!mont)
 407                         goto err;
 408                 }
 409
 410
 411         DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
 412         /* BN_copy(&u1,&t1); */
 413         /* let u1 = u1 mod q */
 414         if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
 415
 416         /* V is now in u1.  If the signature is correct, it will be
 417          * equal to R. */
 418         ret=(BN_ucmp(&u1, sig->r) == 0);
 419
 420         err:
 421         /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
 422            there is no error in BN. Test should be ret == -1 (Ben) */
 423         if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
 424         if (ctx != NULL) BN_CTX_free(ctx);
 425         BN_free(&u1);
 426         BN_free(&u2);
 427         BN_free(&t1);
 428         return(ret);
 429         }
 430
 431 static int dsa_init(DSA *dsa)
 432 {
 433         dsa->flags|=DSA_FLAG_CACHE_MONT_P;
 434         return(1);
 435 }
 436
 437 static int dsa_finish(DSA *dsa)
 438 {
 439         if(dsa->method_mont_p)
 440                 BN_MONT_CTX_free(dsa->method_mont_p);
 441         return(1);
 442 }
 443